1. Field of the Invention
The present invention is generally related to communication systems. More particularly, the present invention is related to cable modem systems and methods for performing Payload Header Verification and Payload Header Suppression (PHS) and Expansion.
2. Related Art
The Data Over Cable System Interface Specification (DOCSIS) introduced the concept of Payload Header Suppression (PHS). Payload header suppression can be divided into a verification portion and a suppression portion. Before allowing suppression, the PHS verification portion compares bytes targeted for suppression against a set of bytes defined for a specific PHS rule. During the suppression portion, the transmitting device uses the PHS Rule to suppress a frequently recurring portion of the payload header of a packet, thereby reducing the amount of data transmitted on the cable. The receiving device restores the header data using a locally stored version of the same PHS rule. Heretofore, cable modems and cable modem termination systems have relied upon software to perform the functions of payload header verification and suppression. Reliance upon software, however, results in significant processing overhead. As a result of this processing overhead, the number of cable modems supportable by a single cable modem termination system is reduced.
Thus, what is needed is an apparatus and method for performing payload header verification, suppression and expansion in hardware such that the performance of the overall system is significantly improved.